Study shows medical marijuana grows drying local watersheds

While illegal marijuana grows often catch the blame for causing environmental damage, results from a four-year state study show that outdoor medical marijuana grows are diverting enough water to suck local watersheds dry.

The study examined flow rates and the number of medical marijuana grows in three Humboldt County watersheds — Salmon Creek and northern and southern Redwood Creek — and Outlet Creek in Mendocino County from 2009 to 2012.

Fish and Wildlife environmental scientist Scott Bauer was struck with the idea for the study four years ago after the department was alerted to a rise in complaints.

"We started getting called out to assess environmental damages of these grows," Bauer said. "We thought, 'Wow, this is happening a lot more frequently.' We thought maybe we should look at this on a larger scale."

Using Google Earth aerial imagery, Bauer began calculating the acreage of land being used for medical marijuana cultivation near each watershed. After comparing acreage data from 2009 through 2012, Bauer made a "striking" discovery.

"In our study, the amount of area being used for cultivation had grown anywhere from 70 to 100 percent," Bauer said. "It essentially doubled."

To calculate the number of cannabis plants being grown in each watershed, Bauer — along with members of county sheriff's offices and the North Coast Water Quality Control Board — visited 32 grow sites. During the site visits, the researchers recorded the spatial arrangement and canopy area of the plants, along with how the water was being obtained.

After the visits, it was estimated that there are roughly 30,000 marijuana plants being grown per watershed. Admitting that aerial imagery is not as accurate as a direct plant count, Bauer said he was confident with the figure.

"The canopy issue was a big one, and we had good sources saying that your numbers are too low," he said. "We obviously missed some plants. The greenhouse issue was also brought up, with people saying, 'Well, what if they're growing tomatoes?' They're in the middle of nowhere, and the market is two hours away. For every greenhouse I've ever been to, that hasn't been the case."

Using Humboldt Growers Association's estimate that each plant requires about 6 gallons of water per day, with a 150-day growing season from June through October, Bauer calculated the total amount of water used from each watershed. He compared that information with flow data from the U.S. Geological Survey.

"If the current level of activity continues, we'll have dry streams and less fish," Bauer said. "We found that in three of four watersheds, that essentially that cultivation could take all the water out of them."

The Humboldt County watershed data showed that water demand for grows exceeded the low flow estimates in both Salmon Creek and the southern Redwood Creek by nearly 250 percent. For upper Redwood Creek, it was 23 percent.

If there is any disruption in low flows, the water warms up and you get all these negative impacts," Bauer said. "It greatly effects survival of juvenile salmon who live in these streams, and sometimes they don't come back. This affects our fisheries, sport fishing, commercial fishing and all the critters."

North Coast Water Board environmental scientist Stormer Feiler said he finds the same problems during his own site visits.

"It breaks up the streams from a continuous flow," Feiler said. "If there is not enough pool depth, that's a limitation for what can live there. We have to have a good amount of summer water for juvenile salmon."

Out of 150 environmental complaints he assesses each year, Feiler said nearly one-third are related to medical marijuana grows.

"Out of those, I get to investigate about half of them," Feiler said. "So far, I have not found a site that is in compliance with the law. These aren't legal grow sites unless they follow environmental regulations."

Despite medical marijuana being legal in California, Humboldt County Sheriff's Office Lt. Wayne Hanson said the methods used to grow the plants are often anything but that.

"Very rarely do I run into a legitimate marijuana grow," Hanson said. "The sheriff's office is not targeting those folks. But if they violate medical marijuana laws in how many plants they are growing or destroying the environment, they will be arrested and criminally charged. They have to face the consequences."

Hanson estimates that there are more than 5,000 medical marijuana grows in the county.

North Coast Water Board Executive Director Matt St. John said that there are no regulations specifically addressing environmental damage caused by medical marijuana grows.

"The State Water Board directed me to develop a regulatory program for the discharges from marijuana operations, and has given us the goal of trying to complete that by the end of this calender year," St. John said.

St. John said water diversion only makes up a portion of the environmental damage caused by grows. Other issues include illegal grading to build roads, fertilizer dumping and the use of rodenticides.

State Water Board spokesman Timothy Moran wrote in an email that there are still regulations in place regarding water diversions.

"Growers whose activities result in an unauthorized discharge to waters of the state, the diversion of water without a water right, and/or who fail to file a Statement of Water Diversion and Use when required could be subject to administrative civil liability of up to $10,000 per day and per violation."

Bauer said he will begin a follow-up study this month examining real-time flow data in the watersheds and measuring how fluctuations affect indicator organisms.

"Little bugs can tell a lot," Bauer said. "You'll lose certain bugs that are sensitive to changing flow patterns. You can compare them to reference watersheds that have no flow issues, and if you see certain bugs are missing, you can pretty much say there is something going on in that watershed."

With these studies, Bauer said he hopes growers will take the steps to come into compliance with environmental law.

"The long story short is we want people to conserve water and get permits," Bauer said. "Doesn't matter if you're growing grapes or tomatoes. It's not about the plant. It's about water quality, which affects us."